CONCHOLOGY. 73 
FAMILY XVI. 
Myritacea. Three genera. 
1. Genus Mytilus. Pl. VIII. 
Animal. Body oval, somewhat inflated; mantle open in its 
inferior half only, and terminated posteriorly by an oval cleft with 
fringed edges ; a linguiform, canaliculated, abdominal appendage, 
with a byssus at its base behind, and several pairs of retractile 
muscles; mouth with simple lips; two contractile muscles, of 
which the anterior is very small. 
Shell. Of a serrated tissue, elongated, more or less oval, some- 
times subtriangular, equivalve, summits anterior, more or less 
curved, sloping inferiorly in a slight degree; hinge toothless, or 
with two very small rudiments; ligament dorsal, linear, subin- 
terior, inserted in a narrow and very long furrow; two muscular 
impressions, of which the anterior is very small, besides those of 
the retractile muscles. Inhabits the British and American seas. 
Forty-two species. 
Mytilus erosus, Mytilus Magellicanus. 
M. decussatus. M. crenatus. 
M. elongatus. M. hirsutus. 
M. Zonarius. M. latus. 
M. violaceus. M. ungulatus. 
M. smaragdinus. M. opalus. 
M. edulis. M. corneus. 
M. Hesperianus. M. retusus. 
M. exustus. M. perna. 
M. ovalis. M. bilocularis. : 
M. Domingensis. M. ustulatus. 
M. Afer. M. Senegalensis. 
M. ungularis. M. achatinus. 
M. borealis. M. planulatus. 
M. augustanus. M. Galloprovincialis. 
M. lacunatus. M. lineatus. 
M. incurvatus. M. canalis. 
M. abbreviatus. M. sanguineus. 
